Attaching Stearman sheet metal fairings with 10/32 screws matching a large array of holes to a similar array of nut plates can be a frustrating job.
The first few holes line up pretty well, but it can go downhill from there. You end up trying to pry the panel hole over a bit with an awl, so you can get the screw through. You try starting the screw in at a slight angle hoping it will straighten up and not cross thread the nut plate. You finally hog out the hole in the panel with a rat tail file until it is sufficiently oblong to provide clearance.
A better way is to take the time to drill out the fixed nut plates and install floating nut plates. Better yet, put the floating plates in the first time.
Floating nut plates provide a nut that can move around a bit in both directions and give you a much wider tolerance in matching up holes with the nut. When tight, they hold just as well as the fixed nut plates.
When you put in a floating nut plate however, you must open up the hole under the nut plate in order to take advantage of the float. You can determine the size of the hole by looking at the bottom of the nut plate and measuring the hole there. The hole in the panel under the plate should be the same size.
A drill guide made just for installing nut plates is a real handy item to have.
Drill a 1/4 inch hole where you want the plate. Push the 1/4 inch pin in the drill guide into the hole and align the side holes in the direction you want the nut plate. Using a #40 drill, drill through the guide on the right of the pin and through the panel.
Lift the drill guide, turn it over, put the 1/4 inch pin back in the same hole, and put the small pin in the #40 hole you just drilled. Now with the #40 drill, drill through the guide hole on the left of the pin and through the panel.
Now you have perfectly matched mounting holes with which to rivet on the nut plate. (The other hole in the drill guide is used for a nut plate that has both mounting holes on the same side of the clearance hole.)
Now look at the back of the nut plate and measure the diameter of the clearance hole in front of the nut.
To get the most good out of the floating nut, increase the 1/4 inch hole to that same diameter before you mount the nut plate. Different nut plates have different amounts of float.
These plates are not as “original” , but sure improve the quality of life in restoration.
This drill jig can be found at ATI in Escondido, CA, 800-284-4460. It is part No. AT518K—1/4. They are under $25, but there is a $35.00 minimum, so get a friend to buy one too